Electrical-heating method.



W. MGA- JOHNSON. ELECTRICAL HEATING METHOD.

' APPLICATION FILED JAN.11,1904.

93?;,7%. Patented Oct.19,1909.

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To all whom it may concern:

WOOLSEY McA. JOHNSON, or 103.91., KANSAS, assrenota TO THE oolv'rrnnons zinc FURNACE GOMPANY, or rmnrroan, ooN'Nno'rIoU'r, A oonronerrorr or core NECTICUT. I

ELECTRICALHEATING METHOD.

. MM L QSZJW L Specification of Letters Patent Itatented Qct. fit},

Application filed January 11, 1904.

c1ial No. 188,544.

character as to-otler a relatively high re- Be it known that l', ll ooLsi-w lilo)... JOIIX- sis-t a are, as above described. SON, a citizen of the United States, residing For a full understainling; ot my invention, at 101a, in the county of Allen and State of reference made to the accompanying Kansas, have invented certain new and usedrawing. wherein one form of electric fur ful Improvements in Electrical Heating" 1 nave suitable tor carrying out my method Methods, oi which the following is a specil is illustrated in vertical section. fication. lin said dr: wing the furnace body is This invention is a 7 method of heating 1 shown as constructed of refractory material materials by means of the electric current. 2. provided with a sheath or casing 2 which In electric furnaces of the type wherein i may be oi metal. Said sheath and lining the temperature necessary for an operation are preferably formed of any ijlesired numof reduction. smelting or melting is devel- 1 her of sec ions 3, the planes of section oped by the passage of a suitable electric being transverse to the direction of passage current through a body of material constioi the current through the charge. Layers tilting the charge to be treatechit is in gen- 1 ol asbestos or other suitable refractory ineral essential that the chamber be provided. salutingiuaterial l are interposed between, with a refractory hearth or lining" which the sections in order to render the furnace is substantially unatl'ected. ly the charge substantially air-tight and to increase the or by the products of the operation, said electrical resistance of the lining. refractory lining being acid, neutral or basic, 1 are electrodes, any desired number in accordance with the character of the ore of wh ch project. in opposed pairs into the or material to be reduced or heated, firefurnace chamber. The. furnace chamber is clay and magnesia being common examples sed y 111 5 of H C C B 5176" of such materials. These materials are in clay or similar material 7, and preferably general poor conductors of electricity at also constructed of insulated sections. 'E'he ordinary temperatures, but at. high tem-- hearth of the furnace shown inclining peratures become capable of carrying conslightly from the electrodes a central, sideraole current, the heatdevelonedthereby transverse trough or depression 8, at one being, however, far less eli'ectively applied end of which a tap-hole 9 may be provided. than that developed within the charge itself 10 represents the usual draw, and 11 an or in immediate proxin'iity thereto. More outlet for vapors; in case the furnace. be over, as the temperature oi the hearth or linused for the distillation of zinc, as hereing increases, its conductivity also increases, inatter more particularly described, any whereby the losses from this source tend to suitable condenser may be provided in conincrease very rapidly. l have discovered nection with said outlet 1 that such losses may be greatly reduced, 01' Means for feeding the charge or body 12 even substantially obviated, by maintaining of high resistance are shown at 13, 13, in contact with the hearth of the furnace comprising suitable conduits, screw conveya body or layer of material of relatively high ers or other mechanical feeding devices resistance, and maintaining above said high therein, and hoppers, which may be fitted resistance body a body of the chargeor mawith closures. The material is forced in terial to be reduced or treated, said body through the conduits 13 by the feeding means being of relatively low resistance. Both the therein, either intermittently or continuously, hi h resistance and low resistance bodies at a sufficient rate to maintain a layer or are preferably maintained in operative conbody of high resistance material between tact with the electrodes, and means are prefsaid charge 15 and the furnace hearth or erably provided for feeding both bodies, lining 3. Upon this layer the charge of relacontinuously or intermittently, to the furtively low resistance is fed through the hopnace chamber. The high resistance body pers 14. Similar means 14,14 are illustrated which is maintained adjacent to the hearth or lining of the furnace, may, in some cases, be a portion of the charge to be reduced, but is of such composition or of such'physical 15 of lower resistance. 1 have indicated. me-

conduits 1%, but these may be omitted it do for the introduction of the charge or body.

chanical feeding devices in. the charging any suitable means may be substithose shown for the introduction l noted that by means of the conn shown the bodies of lower and resistance are maintained in super- 1 layers on the hearth, and that both f said bodies are illustrated as in contact with electrodes. I do not limit myself, however, to the maintenance of the high resistance body 12 in contact with the electrodes. While I prefer to maintain a layer of said high resistance body over the entire hearth of the furnace, this is not essential to my invention. y

it will now describe a specific example of m method, it being understood, however, that any sui )le charges or mixtures may be used i stead those specified. its one such may treat arcs of zinc, substancribcd in my copending applica- No. 188,525, filed January 11, l-lccording to the operation therein described, a ferruginous blende, or low grade are containing iron, zinc and sulfur, is roasted, and thereafter subjected to reducing action such conditions that the iron is reduced to metal in the form of particles this so. .ated throughout the body of the charge, tlie'sinc .ibstantially unreduccd. The c arge is then introduced into the electric mace and the current transmitted through the to raise the temperature to such degree as will suflice for the distillation of he zinc, the reduction of the compound of zinc being efi'ectecl by the iron, or wholly or in part by carbon. or carbonaceous reducmixed with the charge.

A charge of the character above described relatively conductive by reason of themetallic particles disseminated through it, and m y constitute the charge or layer above red to. The charge or layer 12 of high rance, to be introduced at 13 and servas hereinbefore described to preserve the seamefurnace hearth from the full heating effect of the furnace operation, may consist of carbon in any suitable form, or of a mixture of carbon with a suitable ore, or with a compound such as magnesia or siloxicon which is substantially irreducible at the temperature employed.

As other specific examples I may mention that the body 15 may comprise any suitable ore or material to be heated, the ore being preferably mixed with sutficient carbon for its reduction, while the body 12 may comprise the same or another ore or material, which may or may not be mixed with. carbon, it being essential only that the body 12 be oi such composition, or degree of comn'iinution, as to be of relatively high resistance as compared with the body 15. I

.l. have described the hearth or 1mm composed of a material the conductivit which increases with the sire it to bcundcrstood, vention is applicable to any hearth or lining of material which is capable under any conditions of transmitting an electric current.

I claim l. The method of reducing'lealcaqe cur= rent through the walls or lining 01' an electric furnace which consists in feeding between the charge and the Walls or the furnace a granular material having a high electrical resistance relative to that of the charge.

2. The method of reducing leakage of current through the walls or lining of an electric furnace which consists in feeding between the charge and the walls of the fur nace a granular material containing the constituents of the charge but having a high. electrical resistance relative thereto.

In testimony whereof I affix my signature in presence of two witnesses.

l VOOLSEY MoA. JOHNSON.

Witnesses:

T. EWING, A. M. EWING.

as .1 temperature; I dehowever, that my in- 

